import java.util.Arrays;
import java.util.Map;

public class Test {
    public int[][] matrixBlockSum(int[][] mat, int k) {
        int m=mat.length,n=mat[0].length;
        int[][] dp=new int[m+1][n+1];
        for (int i = 1; i <= m; i++) {
            for (int j = 1; j <= n; j++) {
                dp[i][j]=dp[i-1][j]+dp[i][j-1]-dp[i-1][j-1]+mat[i-1][j-1];
            }
        }

        int[][] ret=new int[m][n];
        for (int i = 0; i < m; i++) {
            for (int j = 0; j < n; j++) {
                int x1= Math.max(0,i-k)+1,y1=Math.max(0,j-k)+1;
                int x2= Math.min(m-1,i+k)+1,y2=Math.min(n-1,j+k)+1;
                ret[i][j]=dp[x2][y2]-dp[x1-1][y2]-dp[x2][y1-1]+dp[x1-1][y1-1];
            }
        }
        return ret;
    }

    public static void main(String[] args) {
        int k=1;//假如向外扩展一个
        int[][] mat= {
                {1, 2, 3},
                {4, 5, 6},
                {7, 8, 9}
        };
        Test test=new Test();
        int[][] ret=test.matrixBlockSum(mat,1);

        System.out.println(Arrays.deepToString(ret));
    }
}
